/*
 * Copyright (c) 2004-2022, University of Oslo
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * Neither the name of the HISP project nor the names of its contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.hisp.dhis.datasource;

import com.google.common.collect.Iterators;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import javax.sql.DataSource;
import org.springframework.jdbc.datasource.AbstractDataSource;

/**
 * Data source implementation which routes to the configured target data sources in a circular
 * fashion.
 *
 * @author Lars Helge Overland
 */
public class CircularRoutingDataSource extends AbstractDataSource {
  private Iterator<DataSource> dataSourceIterator;

  public CircularRoutingDataSource() {}

  public CircularRoutingDataSource(List<DataSource> targetDataSources) {
    this.dataSourceIterator = Iterators.cycle(Collections.synchronizedList(targetDataSources));
  }

  // -------------------------------------------------------------------------
  // AbstractDataSource implementation
  // -------------------------------------------------------------------------

  @Override
  public Connection getConnection() throws SQLException {
    return getDataSource().getConnection();
  }

  @Override
  public Connection getConnection(String username, String password) throws SQLException {
    return getDataSource().getConnection(username, password);
  }

  // -------------------------------------------------------------------------
  // Private methods
  // -------------------------------------------------------------------------

  private synchronized DataSource getDataSource() {
    return dataSourceIterator.next();
  }
}
